IBU-DC Phosphoramidite is used for synthesis of oligonucleotides[1].
References
[1] Chi Fu, et al. Identification and quantification of protecting groups remaining in commercial oligonucleotide products using monoclonal antibodies. Anal Biochem. 2002 Jul 1;306(1):135-43. DOI:10.1006/abio.2002.5687